Radioactive isotope dating rocks
Say a second friend who is aware of this arrangement visits and notices that your carton of ice cream contains 70 raisins and 10 chocolate chips.
She declares, "I guess you went shopping about three days ago." How does she know this?
This is because when radioactive elements first come into being, they are presumed to consist entirely of a single isotope.
Imagine that you enjoy a certain kind of ice cream flavored with chocolate chips.
Be aware also that for many centuries, most human "knowledge" of the age of rocks, formations such as the Grand Canyon, and everything else around you was predicated on the Genesis account of the Bible, which posits that the entire cosmos is perhaps 10,000 years old.
Uranium-lead (U-Pb) dating: Radioactive uranium comes in two forms, uranium-238 and uranium-235.